For witnessing or attesting a signature: State of Washington. An acknowledgment is one of the most common types of notarial acts, but it often confuses Notaries.Here are 5 steps to performing an acknowledgment. A Washington notary acknowledgment form is used to officially authenticate a signature on a legal document. The short-form acknowledgment certificate is used when an individual is signing and acknowledging on his or her own behalf. Download a notary acknowledgment form in PDF or Word format.